Some Judgments of Perception

I wa n t to raise some childishly simple questions as to what we are doing when we make judgments of a certain kind, which we all do in fact exceedingly commonly make. The kind of judgments I mean are those which we make when, with regard to something which we are seeing, we judge such things as “That is an inkstand,” “That is a tablecloth,” “That is a door,” etc., etc.; or when, with regard to something which we are feeling with our hands, we judge such things as “This is cloth,” “This is a finger,” “This is a coin,” etc., etc.

It is scarcely possible, I think, to exaggerate the frequency with which we make such judgments as these, nor yet the certainty with which we are able to make vast numbers of them. Any man, who is not blind, can, at almost any moment of his waking life, except when he is in the dark, make a large number of judgments of the first kind, with the greatest certainty. He has only to look about him, if he is indoors, to judge with regard to various things which he is seeing, such things as “That is a window,” “That is a chair,” “This is a book”; or, if he is out-of-doors, such things as “That is a house,” “That is a motor-car,” “That is a man,” or “That is a stone,” “That is a tree,” “That is a cloud.” And all of us, who are not blind, do in fact constantly make such judgments, even if, as a rule, we only make them as parts of more complicated judgments. What I mean is that, when we make such judgments as “Hullo! that clock has stopped,” or “This chair is more comfortable than that one,” or “That man looks like a foreigner,” judgments of the simpler kind with which I am concerned are, so far as I can see, actually a part of what we are judging. In judging “That clock has stopped,” part of what I am actually judging is, so far as I can see, “That is a clock;” and similarly if I judge “That tree is taller than this one,” my judgment actually contains the two simpler judgments “That is a tree,” and “This is a tree.” Perhaps most judgments which we make, of the kind I mean, are, in this way, only parts of more complicated judgments: I do not know whether this is so or not. But in any case there can be no doubt that we make them exceedingly commonly. And even a blind man, or a man in the dark, can and does, very frequently, make judgments of the second kind— judgments about things which he is feeling with his hands. All of us, for instance, at almost any moment of our waking life, whether we are in the dark or not, have only to feel certain parts of our own bodies or of our clothes, in order to make, with great certainty, such judgments as “This is a finger,” “This is a nose,” “This is cloth.” And similarly I have only to feel in my pockets to judge, with regard to objects which I meet with there, such things as “This is a coin,” “This is a pencil,” “This is a pipe.”

Judgments of this kind would, I think, commonly, and rightly, be taken to be judgments, the truth of which involves the existence of material things or physical objects. If I am right in judging that this is an inkstand, it follows that there is at least one inkstand in the Universe; and if there is an inkstand in the Universe, it follows that there is in it at least one material thing or physical object. This may, of course, be disputed. Berkeley, if I understand him rightly, was clearly of opinion that there was no inconsistency in maintaining that there were in the Universe thousands of inkstands and trees and stones and stars, and that yet there was in it no such thing as matter. And perhaps the definition of matter, which he adopted, was such that there really was no inconsistency in maintaining this. Perhaps, similarly, other philosophers have sometimes adopted definitions of the expressions “material things” and “physical objects,” which were such that all the judgments of this kind that we make might quite well be true, without its being true that there are in the Universe any material things whatever. Perhaps, even, there may be some justification for adopting definitions of those terms which would yield the surprising result that we may, with perfect consistency, maintain that the world is full of minerals and vegetables and animals, of all sorts of different kinds, and that yet there is not to be found in it a single material thing. I do not know whether there is or is not any utility in using the terms “material thing” or “physical object” in such a sense as this. But, whether there is or not, I cannot help thinking that there is ample justification for using them in another sense—a sense in which from the proposition that there are in the Universe such things as inkstands or fingers or clouds, it strictly follows that there are in it at least as many material things, and in which, therefore, we can not consistently maintain the existence of inkstands, fingers, and clouds, while denying that of material things. The kinds of judgment which I have mentioned, and thousands of others which might easily be mentioned, are obviously all of the same sort in one very important respect—a respect in which, for instance, such judgments as “This is an emotion,” “This is a judgment,” “This is a colour,” are not of the same sort as they are. And it seems to me that we are certainly using the term “material thing ” in a correct and useful way, if we express this important common property which they have, by saying that of each of them the same can truly be said as was said of the judgment “That is an inkstand”: that, just as from the proposition “There is an inkstand” it follows that there is at least one material thing, so from the proposition “There is a tablecloth,” it follows that there is at least one material thing; and similarly in all the other cases. We can certainly use the expression “Things such as inkstands, tablecloths, fingers, clouds, stars, etc.,” to mean things such as these in a certain very important respect, which we all understand, though we may not be able to define it. And the term “material thing” certainly is and can be correctly used to mean simply things such as these in that respect—whatever it may be. Some term is certainly required to mean merely things such as these in that important respect; and, so far as I can see, there is no term which can be naturally used in this sense except the term “material things” and its equivalents. Thus understood, the term “material thing” certainly does stand for an important notion, which requires a name.

And, if we agree to use the term in this sense, then it is obvious that no more can be necessary for the truth of the assertion that there are material things, than is necessary for the truth of judgments of the kind with which I propose to deal. But no more can be necessary for the truth of these judgments than is actually asserted in or logically implied by them. And if we approach the question what is necessary for the truth of the assertion that there are material things, by asking what it is that we actually assert when we make such judgments as these, certain reasons for doubting how much is necessary are, I think, brought out much more clearly, than if we approach the question in any other way. Many philosophers have told us a very great deal as to what they suppose to be involved in the existence of material things; and some, at least, among them seem to have meant by “material things” such things as inkstands, fingers and clouds. But I can think of only one type of view as to the constitution of material things, which is such that it is tolerably clear what answer those who hold it would give to the simple question; What is it that I am judging, when I judge, as I now do, that that is an ink-stand? The type of view I mean is that to which the view that Mill suggests, when he explains what he means by saying that Matter is a Permanent Possibility of Sensation, and also the view or views which Mr. Russell seems to suggest in his “Our Knowledge of the External World,” seem to belong. In the case of views of this kind, it is, I think, tolerably clear what answer those who hold them would give to all the questions I want to raise about judgments of the kind I have described. But it does not seem to me at all certain that any view of this type is true; and certainly many philosophers have held and do hold that all views of this type arc false. But in the case of those who do hold them to be false, I do not know, in any single case, what answer would be given to all the questions which I want to raise. In the case of philosophers, who do not accept any view of the Mill-Russell type, none, so far as I know, has made it clear what answer he would give to all my questions: some have made it clear what answer they would give to some of them; but many, I think, have not even made it clear what answer they would give to any. Perhaps there is some simple and satisfactory answer, which has escaped me, that such philosophers could give to all my questions; but I cannot help thinking that assumptions as to the nature of material things have too often been made, without its even occurring to those who made them to ask, what, if they were true, we could be judging when we make such judgments as these; and that, if this question had been asked, it would have become evident that those assumptions were far less certain than they appeared to be.

I do not know that there is any excuse whatever for calling all judgments of the kind I mean “judgments of perception.” All of them are, of course, judgments about things which we are at the moment perceiving, since, by definition, they are judgments about things which we are seeing or feeling with our hands; and all of them are, no doubt, also based upon something which we perceive about the thing in question. But the mere fact that a judgment is both about a thing which I am perceiving, and also based upon something which I perceive about that thing, does not seem to be a sufficient reason for calling it a judgment of perception; and I do not know that there is any other reason than this for calling all judgments of the kind I mean judgments of perception. I do not want therefore, to assert that all of them are so. But it seems to me quite plain that enormous numbers of them are so, in a perfectly legitimate sense. This judgment, which I now make, to the effect that that is a door, seems to me quite plainly to be a judgment of perception, in the simple sense that I make it because I do, in fact, see that that is a door, and assert in it no more than what I see; and what I see I, of course, perceive. In every case in which I judge, with regard to something which I am seeing or feeling with my hands, that it is a so-and-so, simply because I do perceive, by sight or touch, that it is in fact a thing of that kind, we can, I think, fairly say that the judgment in question is a judgment of perception. And enormous numbers of judgments of the kind I mean are, quite plainly, judgments of perception in this sense. They are not all, for the simple reason that some of them are mistaken. I may, for instance, judge, with regard to an animal which I see at a distance, that it is a sheep, when in fact it is a pig. And here my judgment is certainly not due to the fact that I see it to be a sheep; since I cannot possibly see a thing to be a sheep, unless it is one. It, therefore, is not a judgment of perception in this sense. And moreover, even where such a judgment is true, it may not always be a judgment of perception, for the reason that, whereas I only see the thing in question, the kind of thing which I judge it to be is of such a nature, that it is impossible for any one, by sight alone, to perceive anything to be of that kind. How to draw the line between judgments of this kind, which are judgments of perception, and those which are not, I do not know. That is to say, I do not know what conditions must be fulfilled in order that I may be truly said to be perceiving, by sight or touch, such things as that that is a door, this is a finger, and not merely inferring them. Some people may no doubt think that it is very unphilosophical in me to say that we ever can perceive such things as these. But it seems to me that we do, in ordinary life, constantly talk of seeing such things, and that, when we do so, we are neither using language incorrectly, nor making any mistake about the facts—supposing something to occur which never does in fact occur. The truth seems to me to be that we are using the term “perceive” in a way which is both perfectly correct and expresses a kind of thing which constantly does occur, only that some philosophers have not recognised that this is a correct usage of the term and have not been able to define it. I am not, therefore, afraid to say that I do now perceive that that is a door, and that that is a finger. Only, of course, when I say that I do, I do not mean to assert that part of what I “perceive,” when I “perceive” these things, may not be something which, in an important sense, is known to me only by inference. It would be very rash to assert that “perception,” in this sense of the word, entirely excludes inference. All that seems to me certain is that there is an important and useful sense of the word “perception,” which is such that the amount and kind of inference, if inference there be, which is involved in my present perception that that is a door, is no bar to the truth of the assertion that I do perceive that it is one. Vast numbers, then, of the kind of judgments with which I propose to deal seem to me to be, in an important and legitimate sense, judgments of perception; although I am not prepared to define, any further than I have done, what that sense is. And though it is true that the questions which I shall raise apply just as much to those of them which are not judgments of perception as to those which are, it is, of course, also true that they apply just as much to those which are as to those which are not; so that I shall be really dealing with a large and important class among judgments of perception.

It is true that, if certain views which, if I understand them rightly, some Philosophers have seriously entertained, were true ones, it would be quite impossible that any of them should be judgments of perception. For some philosophers seem to me to have denied that we ever do in fact know such things as these, and others not only that we ever know them but also that they are ever true. And, if, in fact, I never do know such a thing, or if it is never true, it will of course, follow that I never perceive such a thing; since I certainly cannot, in this sense, perceive anything whatever, unless I both know it and it is true. But it seems to me a sufficient refutation of such views as these, simply to point to cases in which we do know such things. This, after all, you know, really is a finger: there is no doubt about it: I know it, and you all know it. And I think we may safely challenge any philosopher to bring forward any argument in favour either of the proposition that we do not know it, or of the proposition that it is not true, which does not at some point, rest upon some premiss which is, beyond comparison, less certain than is the proposition which it is designed to attack. The questions whether we do ever know such things as these, and whether there are any material things, seem to me, therefore, to be questions which there is no need to take seriously: they are questions which it is quite easy to answer, with certainty, in the affirmative. What does, I think, need to be taken seriously, and what is really dubious, is not the question, whether this is a finger, or whether I know that it is, but the question what, in certain respects, I am knowing, when I know that it is. And this is the question to which I will now address myself.

To begin with there is one thing which seems to me to be very certain indeed about such judgments. It is unfortunately a thing which I do not know how properly to express. There seem to me to be objections to every way of expressing it which I can think of. But I hope I may be able to make my meaning clear, in spite of the inadequacy of my expression. The thing I mean is a thing which may to some people seem so obvious as to be scarcely worth saying. But I cannot help thinking that it is not always clearly recognised, and even that some philosophers, to judge from what they say, might perhaps dispute it. It seems to me to be an assumption which is silently made in many treatments of the subject, and, as I say, it seems to me to be very certain indeed. But I think it is at all events worth while to try to make the assumption explicit, in case it should be disputed. If it really is not true, then the other questions to which I shall go on, and which seem to me really dubious and difficult, do not, I think, arise at all.

I will try to express this fundamental assumption, which seems to me so very certain, by saying it is the assumption that, in all cases in which I make a judgment of this sort, I have no difficulty whatever in picking out a thing, which is, quite plainly, in a sense in which nothing else is, the thing about which I am making my judgment; and that yet, though this thing is the thing about which I am judging, I am, quite certainly, not, in general, judging with regard to it, that it is a thing of that kind for which the term, which seems to express the predicate of my judgment, is a name. Thus, when I judge, as now, that That is an inkstand, I have no difficulty whatever in picking out, from what, if you like, you can call my total field of presentation at the moment, an object, which is undoubtedly, in a sense in which nothing else is, the object about which I am making this judgment; and yet it seems to me quite certain that of this object I am not judging that it is a whole inkstand. And similarly when I judge, with regard to something which I am feeling in my pocket, “This is a coin,” I have no difficulty in picking out, from my field of presentation, an object, which is undoubtedly the object with which my judgment is concerned; and yet I am certainly not judging with regard to this object that it is a whole coin. I say that always, when I make such a judgment, I can pick out the one, among the objects presented to me at the time, about which I am making it; but I have only said that in general I am not judging with regard to this object that it is a thing of the kind, for which the term, which seems to express the predicate of my judgment, is a name. And I have limited my second proposition in this way, because there are cases, in which it does not, at first sight, seem quite so certain that I am not doing this, as in the two instances I have just given. When, for instance, I judge with regard to something, which I am seeing, “This is a soap-bubble,” or “This is a drop of water,” or even when I judge “This is a spot of ink,” it may not seem quite so plain, that I may not be judging, with regard to the very object presented to me, that it is, itself, a whole soap-bubble, a whole drop of water, or a whole spot of ink, as it always is, in the case of an inkstand, or a coin, that I never take the presented object, about which I am judging, to be a whole inkstand, or a whole coin. The sort of reason why I say this will, of course, be obvious to any one, and it is obviously of a childish order. But I cannot say that it seems to me quite obvious that in such a case I am not judging of the presented object that it is a whole drop of water, in the way in which it does seem to be obvious that I am not judging of this presented object that it is an inkstand. That is why I limit myself to saying that, in general, when I judge “That is a so-and-so” I am not judging with regard to the presented object, about which my judgment is that it is a thing of the kind in question. As much as this seems to me to be a thing which any child can see. Nobody will suppose, for a moment, that when he judges such things as “This is a sofa,” or “This is a tree,” he is judging, with regard to the presented object about which his judgment plainly is, that it is a whole sofa or a whole tree: he can, at most, suppose that he is judging it to be a part of the surface of a sofa or a part of the surface of a tree. And certainly in the case of most judgments of this kind which we make, whether in the case of all or not, this is plainly the case: we are not judging, with regard to the presented object about which our judgment plainly is, that it is a thing of the kind, for which the term which appears to express the predicate of our judgment, is a name. And that this should be true of most judgments of this kind, whether of all or not, is quite sufficient for my purpose.

This much, then, seems to me to be very certain indeed. But I will try to make clearer exactly what I mean by it, by mentioning a ground on which I imagine it might perhaps be disputed.

The object of which I have spoken as the object, about which, in each particular case, such a judgment as this always is a judgment, is, of course, always an object of the kind which some philosophers would call a sensation, and others would call a sense-datum. Whether all philosophers, when they talk of sensations, mean to include among them such objects as these, I do not know. Some, who have given a great deal of attention to the subject, and for whom I have a great respect, talk of sensations in such a way, that I cannot be sure what they are talking about at all or whether there are such things. But many, I think, undoubtedly do mean to include such subjects as these. No doubt, in general, when they call them sensations, they mean to attribute to them properties, which it seems to me extremely doubtful whether they possess. And perhaps even those who call them sense-data, may, in part, be attributing to them properties which it may be doubtful whether they possess. If we want to define a sensation or a sense-datum, in a manner which will leave it not open to doubt what sort of things we are talking of, and that there are such things, I do not know that we can do it better than by saying that sense-data are the sort of things, about which such judgments as these always seem to be made—the sort of things which seem to be the real or ultimate subjects of all such judgments. Such a way of defining how the term “sense-datum” is used, may not seem very satisfactory; but I am inclined to think it may be as satisfactory as any which can be found. And it is certainly calculated to obviate some misunderstandings which may arise; since everybody can see, I think, what the thing is which I am describing as the thing about which he is making his judgment, when he judges “That is an inkstand,” and that there is such a thing, even if he does not agree that this description applies to it.

I can, in fact, imagine that some of those who would call this thing a sensation would deny that my judgment is about it at all. It would sometimes be spoken of as the sensation which mediates my perception of this inkstand in this instance. And I can imagine that some of those who would so speak of it might be inclined to say that when I judge “This is an inkstand,” my judgment is about this inkstand which I perceive, and not, in any sense at all, about the sensation which mediates my perception of it. They may perhaps imagine that the sensation mediates my perception of the inkstand only in the sense that it brings the inkstand before my mind in such a way that, once it is before my mind, I can make a judgment about it, which is not a judgment about the mediating sensation at all; and that such a judgment is the one I am actually expressing when I say “This is an inkstand.” Such a view, if it is held, seems to me to be quite certainly false, and is what I have intended to deny. And perhaps I can put most clearly the reason why it seems to me false, by saying that, if (which may be doubted) there is anything which is this inkstand, that thing is certainly not given to me independently of this sense-datum, in such a sense that I can possibly make a judgment about it which is not a judgment about this sense-datum. I am not, of course, denying that I do perceive this inkstand, and that my judgment is, in a sense, a judgment about it. Both these things seem to me to be quite obviously true. I am only maintaining that my judgment is also, in another sense, a judgment about this sense-datum which mediates my perception of the inkstand. Those who say that this sense-datum does mediate my perception of the inkstand, would, of course, admit that my perception of the inkstand is, in a sense, dependent upon the sense-datum; that it is dependent is implied in the mere statement that it is mediated by it. But it might be maintained that it is dependent on it only in the sense in which, when the idea of one object is called up in my mind, through association, by the idea of another, the idea which is called up is dependent on the idea which calls it up. What I wish to maintain, and what seems to me to be quite certainly true, is that my perception of this inkstand is dependent on this sense-datum, in a quite different and far more intimate sense than this. It is dependent on it in the sense that, if there is anything which is this inkstand, then, in perceiving that thing, I am knowing it only as the thing which stands in a certain relation to this sense-datum. When the idea of one object is called up in my mind by the idea of another, I do not know the second object only as the thing which has a certain relation to the first: on the contrary, I can make a judgment about the second object, which is not a judgment about the first. And similarly in the case of two sense-data which are presented to me simultaneously, I do not know the one only as a thing which has a certain relation to the other. But in the case of this sense-datum and th is inkstand the case seems to me to be plainly quite different. If there be a thing which is this inkstand at all, it is certainly only known to me as the thing which stands in a certain relation to this sense-datum. It is not given to me, in the sense in which this sense-datum is given. If there be such a thing at all, it is quite certainly only known to me by description, in the sense in which Mr. Russell uses that phrase; and the description by which it is known is that of being the thing which stands to this sense-datum in a certain relation. That is to say, when I make such a judgment as “This inkstand is a good big one”; what I am really judging is: “There is a thing which stands to this in a certain relation, and which is an inkstand, and that thing is a good big one” —where “this” stands for this presented object. I am referring to or identifying the thing which is this inkstand, if there be such a thing at all, only as the thing which stands to this sense-datum in a certain relation; and hence my judgment, though in one sense it may be said to be a judgment about the inkstand, is quite certainly also, in another sense, a judgment about this sense-datum. This seems to me so clear, that I wonder how anyone can deny it; and perhaps nobody would. But I cannot help thinking that it is not clear to everybody; partly because, so far as I can make out, nobody before Mr. Russell had pointed out the extreme difference there is between a judgment about a thing known only by description to the individual who makes the judgment, and a judgment about a thing not known to him only in this way; and partly because so many people seem still utterly to have failed to understand what the distinction is which he expresses in this way. I will try to make the point clear, in a slightly different way. Suppose I am seeing two coins, lying side by side, and am not perceiving them in any other way except by sight.

It will be plain to everybody, I think, that, when I identify the one as “This one” and the other as “That one,” I identify them only by reference to the two visual presented objects, which correspond respectively to the one and to the other. But what may not, I think, be realised, is that the sense in which I identify them by reference to the corresponding sense-data, is one which involves that every judgment which I make about the one is a judgment about the sense-datum which corresponds to it, and every judgment I make about the other, a judgment about the sense-datum which corresponds to it: I simply cannot make a judgment about either, which is not a judgment about the corresponding sense-datum. But if the two coins were given to me, in the sense in which the two sense-data are, this would certainly not be the case. I can identify and distinguish the two sense-data directly, this as this one, and that as that one: I do not need to identify either as the thing which has this relation to this other thing. But I certainly cannot thus directly identify the two coins. I have not four things presented to me (1) this sense-datum, (2) that sense-datum, (3) this coin, and (4) that coin, but two only—this sense-datum and that sense-datum. When, therefore, I judge “This is a coin,” my judgment is certainly a judgment about the one sense-datum, and when I judge “And that is also a coin,” it is certainly a judgment about the other. Only, in spite of what my language might seem to imply, I am certainly not judging either of the one sense-datum that it is a whole coin, nor yet of the other that it is one.

This, then, seems to me fundamentally certain about judgments of this kind. Whenever we make such a judgment we can easily pick out an object (whether we call it a sensation or a sense-datum, or not), which is, in an easily intelligible sense, the object which is the real or ultimate subject of our judgment; and yet, in many cases at all events, what we are judging with regard to this object is certainly not that it is an object of the kind, for which the term which appears to express the predicate of our judgment is a name.

But if this be so, what is it that I am judging, in all such cases, about the presented object, which is the real or ultimate subject of my judgment? It is at this point that we come to questions which seem to me to be really uncertain and difficult to answer. To begin with, there is one answer which is naturally suggested by the reason I have given for saying that, in this case, it is quite obvious that I am not judging, with regard to this presented object, that it is an inkstand, whereas it is not in the same way, quite obvious that, in making such a judgment as “This is a soap-bubble” or “This is a drop of water,” I may not be judging, of the object about which my judgment is, that that very object really is a soap-bubble or a drop of water. The reason I gave is that it is quite obvious that I do not take this presented object to be a whole inkstand: that, at most, I only take it to be part of the surface of an inkstand. And this reason naturally suggests that the true answer to our question may be that what I am judging of the presented object is just that it is a part of the surface of an inkstand. This answer seems to me to be obviously on quite a different level from the suggestion that I am judging it really to be an inkstand. It is not childishly obvious that I am not judging it to be part of the surface of an inkstand, as it is that I am not judging it to be an inkstand—a whole one.

On this view, when I say such things as “That is an inkstand,” “That is a door,” “This is a coin,” these expressions would really only be a loose way of saying “That is part of the surface of an ink-stand,” “That is part of the surface of a door,” “This is part of the surface of a coin.” And there would, I think, plainly be nothing surprising in the fact that we should use language thus loosely. What, at first sight, appears to be a paradox, namely that, whereas I appear to be asserting of a given thing that it is of a certain kind, I am not really asserting of the thing in question that it is of that kind at all, would be susceptible of an easy explanation. And moreover, if this view were true, it would offer an excellent illustration of the difference between a thing known only by description and a thing not so known, and would show how entirely free from mystery that distinction is. On this view, when I judge “That inkstand is a good big one” I shall in effect be judging: “There is one and only one inkstand of which this is part of the surface, and the inkstand of which this is true is a good big one.” It would be quite clear that the part of the surface of the inkstand was given to me in a sense in which the whole was not, just as it is in fact clear that I do now “see” this part of the surface of this inkstand, in a sense in which I do not “see” the whole; and that my judgment, while it is, in fact, about both the whole inkstand, and also about one particular part of its surface, is about them in two entirely different senses.

This view is one, which it is at first sight, I think, very natural to suppose to be true. But before giving the reasons, why, nevertheless, it seems to me extremely doubtful, I think it is desirable to try to explain more precisely what I mean by it. The word “part” is one which is often used extremely vaguely in philosophy; and I can imagine that some people would be willing to assent to the proposition that this sense-datum really is, in some sense or other, a “part” of this inkstand, and that what I am judging with regard to it, when I judge “This is an inkstand,” is, in effect, “There is an inkstand, of which this is a part,” who would be far from allowing that this can possibly be what I am judging, when once they understand what the sense is in which I am here using the word “part.” What this sense is, I am quite unable to define; but I hope I may be able to make my meaning sufficiently clear, by giving instances of things which are undoubtedly “parts” of other things in the sense in question. There is, it seems to me, a sense of the word “part,” in which we all constantly use the word with perfect precision, and, which, therefore, we all understand very well, however little we may be able to define it. It is the sense in which the trunk of any tree is undoubtedly a part of that tree; in which this finger of mine is undoubtedly a part of my hand, and my hand a part of my body. This is a sense in which every part of a material thing or physical object is itself a material thing or physical object; and it is, so far as I can see, the only proper sense in which a material thing can be said to have parts. The view which I wish to discuss is the view that I am judging this presented object to be a part of an inkstand, in this sense. And the nature of the view can perhaps be brought out more clearly, by mentioning one important corollary which would follow from it. I am, of course, at this moment, seeing many parts of the surface of this inkstand. But all these parts, except one, are, in fact, themselves parts of that one. That one is the one of which we should naturally speak as “the part of the surface that I am now seeing” or as “this part of the surface of this inkstand.” There is only one part of the surface of this inkstand, which does thus contain, as parts, all the other parts that I am now seeing. And, if it were true that I am judging this presented object to be a part of the surface of an inkstand at all, in the sense I mean, it would follow that this presented object must, if my judgment “This is an inkstand” be true (as it certainly is), be identical with this part, which contains all the other parts which I am seeing; since there is plainly no other part with which it could possibly be identified. That is to say, if I am really judging of this presented object that it is part of the surface of an inkstand, in the sense I mean, it must be the case that everything which is true of what I should call “this part of the surface of this inkstand” is, in fact, true of this presented object.

This view, therefore, that what we are judging of the ultimate subject of our judgment, when we judge “This is a so-and-so,” is, in general, merely that the subject in question is a part of a thing of the kind in question, can, I think, be most clearly discussed, by asking whether, in this case, this presented object can really be identical with this part of the surface of this inkstand. If it can’t, then most certainly I am not judging of it that it is a part of the surface of an inkstand at all. For my judgment, whatever it is, is true. And yet, if this presented object is not identical with this part of the surface of this inkstand, it certainly is not a part of an inkstand at all; since there is no other part, either of this inkstand or of any other, with which it could possibly be supposed to be identical.

Can we, then, hold that this sense-datum really is identical with this part of the surface of this inkstand? That everything which is true of the one is true of the other?

An enormous number of very familiar arguments have been used by various philosophers, which, if they were sound, would show that we can not. Some of these arguments seem to me to be quite clearly not sound—all, for instance, which rest either on the assumption that this sense-datum can only exist so long as it is perceived, or on the assumption that it can only exist so long as it is perceived by me. Of others I suspect that they may have some force, though I am quite unable to see that they have any. Such, for instance, are all those which assume either that this sense-datum is a sensation or feeling of mine, in a sense which includes the assertion that it is dependent on my mind in the very same sense in which my perception of it obviously is so; or that it is causally dependent on my body in the sense in which my perception of it admittedly is so. But others do seem to me to have great force. I will, however, confine myself to trying to state one, which seems to me to have as much as any. It will be found that this one involves an assumption, which does seem to me to have great force, but which yet seems to me to be doubtful. So far as I know, all good arguments against the view that this sense-datum really is identical with this part of the surface of the inkstand, do involve this same assumption, and have no more force than it has. But in this, of course, I may be wrong. Perhaps some one will be able to point out an argument, which is obviously quite independent of it, and which yet has force.

The argument I mean involves considerations which are exceedingly familiar, so familiar that I am afraid every one may be sick of hearing them alluded to. But, in spite of this fact, it seems to me not quite easy to put it quite precisely, in a way which will distinguish it clearly from other arguments involving the same familiar considerations, but which do not seem to me to be equally cogent. I want, therefore, to try to put it with a degree of precision, which will prevent irrelevant objections from being made to it—objections which would, I think, be relevant against some of these other arguments, but are not, I think, relevant against it.

The fact is that we all, exceedingly commonly, when, at each of two times, separated by a longer or shorter interval, we see a part of the surface of a material thing, in the sense in which I am now seeing this part of the surface of this inkstand, or when at one time we see such a surface and at another perceive one by touch, make, on the second occasion, the judgment “This part of a surface is the same part of the surface of the same thing, as that which I was seeing (or perceiving by touch) just now.” How commonly we all do this can scarcely be exaggerated. I look at this inkstand, and then I look again, and on the second occasion I judge “This part of the surface of this inkstand is the same as, or at least contains a part which is the same as a part of, the part of its surface which I was seeing just now.” Or I look at this finger and then I touch it, and I judge, on the second occasion, “This part of the surface of this finger is the same as one of those I was seeing just now.” We all thus constantly identify a part of a surface of a material thing which we are perceiving at one time with a part which we were perceiving at another.

Now, when we do this—when we judge “This is the same part of the same thing as I was seeing or touching just now,” we, of course, do not mean to exclude the possibility that the part in question may have changed during the interval; that it is really different, on the second occasion, either in shape or size or quality, or in all three, from what it was on the first. That is to say, the sense of sameness which we are here concerned with is one which clearly does not exclude change. We may even be prepared to assert, on general grounds, in all such cases, that the surface in question certainly must have changed. But nevertheless there is a great difference in one respect, between two kinds of such cases, both of which occur exceedingly commonly. If I watch somebody blowing air into a child’s balloon, it constantly happens, at certain stages in the process, that I judge with regard to the part of the surface which I am seeing at that stage, not only that it is larger than it was at an earlier stage, but that it is perceptibly larger. Or, if I pull the face of an india-rubber doll, I may judge at a certain stage in the process that the patch of red colour on its cheek not only is different in shape from what it was at the beginning, but is perceptibly so; it may, for instance, be a perceptibly flatter ellipse than it was to start with. Or, if I watch a person blushing, I may judge at a certain stage that a certain part of the surface of his face not only is different in colour from what it was, when I saw it before he began to blush, but is perceptibly so—perceptibly redder. In enormous numbers of cases we do thus judge of a surface seen at a given time that it is thus perceptibly different in size, or in shape, or in colour, from what it was when we saw it before. But cases are at least equally numerous in which, though we might, on general grounds be prepared to assert that it must have changed in some respect, we should not be prepared to assert that it had, in any respect whatever, changed perceptibly. Of this part of this surface of this inkstand, for instance, I am certainly not prepared to assert that it is now perceptibly different in any respect from what it was when I saw it just now. And similar cases are so numerous that I need not give further instances. We can, therefore, divide cases, in which we judge, of a part of a surface which we are seeing, “This is the same part of the surface of the same material thing as the one I saw just now,” into cases where we should also judge “But it is perceptibly different from what it was then,” and cases in which, even though we might assert “It must be different,” we are certainly not prepared to assert that it is perceptibly so.

But now let us consider the cases in which we are not prepared to assert that the surface in question has changed perceptibly. The strange fact, from which the argument I mean is drawn, is that, in a very large number of such cases, it seems as if it were unmistakably true that the presented object, about which we are making our judgment when we talk of “This surface” at the later time, is perceptibly different, from that about which we are making it when we talk of the surface I saw just now. If, at the later time, I am at a sufficiently greater distance from the surface, the presented object which corresponds to it at the time seems to be perceptibly smaller, than the one which corresponded to it before. If I am looking at it from a sufficiently oblique angle, the later presented object often seems to be perceptibly different in shape—a perceptibly flatter ellipse, for instance. If I am looking at it, with blue spectacles on, when formerly I had none, the later presented object seems to be perceptibly different in colour from the earlier one. If I am perceiving it by touch alone, whereas formerly I was perceiving it by sight alone, the later presented object seems to be perceptibly different from the earlier, in respect of the fact that it is not coloured at all, whereas the earlier was, and that, on the other hand, it has certain tactual qualities, which the earlier had not got. All this seems to be as plain as it can be, and yet it makes absolutely no difference to the fact that of the surface in question we are not prepared to judge that it is perceptibly different from what it was. Sometimes, of course, where there seems to be no doubt that the later presented object is perceptibly different from the earlier, we may not notice that it is so. But even where we do notice the apparent difference, we do still continue to judge of the surface in question: This surface is not, so far as I can tell with certainty by perception, in any way different from what it was when I saw it or touched it just now; I am not prepared to assert that it has changed perceptibly. It seems, therefore, to be absolutely impossible that the surface seen at the later time should be identical with the object presented then, and the surface seen at the earlier identical with the object presented then, for the simple reason that, whereas with regard to the later seen surface I am not prepared to judge that it is in any way perceptibly different from that seen earlier, it seems that with regard to the later sense-datum I cannot fail to judge that it is perceptibly different from the earlier one: the fact that they are perceptibly different simply stares me in the face. It seems, in short, that when, in such a case, I judge: “This surface is not, so far as I can tell, perceptibly different from the one I saw just now,” I cannot possibly be judging of the presented object “This is not, so far as I can tell, perceptibly different from that object which was presented to me just now,” for the simple reason that I can tell, as certainly, almost, as I can tell anything, that it is perceptibly different.

That is the argument, as well as I can put it, for saying that this presented object, is not identical with this part of the surface of this inkstand; and that, therefore, when I judge “This is part of the surface of an inkstand,” I am not judging of this presented object, which nevertheless is the ultimate subject of my judgment, that it is part of the surface of an inkstand. And this argument does seem to me to be a very powerful one.

But nevertheless it does not seem to me to be quite conclusive, because it rests on an assumption, which, though it seems to me to have great force, does not seem to me quite certain. The assumption I mean is the assumption that, in such cases as those I have spoken of, the later presented object really is perceptibly different from the earlier. This assumption has, if I am not mistaken, seemed to many philosophers to be quite unquestionable; they have never even thought of questioning it; and I own that it used to be so with me. And I am still not sure that I may not be talking sheer nonsense in suggesting that it can be questioned. But, if I am, I am no longer able to see that I am. What now seems to me to be possible is that the sense-datum which corresponds to a tree, which I am seeing, when I am a mile off, may not really be perceived to be smaller than the one, which corresponds to the same tree, when I see it from a distance of only a hundred yards, but that it is only perceived to seem smaller; that the sense-datum which corresponds to a penny, which I am seeing obliquely, is not really perceived to be different in shape from that which corresponded to the penny, when I was straight in front of it, but is only perceived to seem different—that all that is perceived is that the one seems elliptical and the other circular; that the sense-datum presented to me when I have the blue spectacles on is not perceived to be different in colour from the one presented to me when I have not, but only to seem so; and finally that the sense-datum presented when I touch this finger is not perceived to be different in any way from that presented to me when I see it, but only to seem so—that I do not perceive the one to be coloured and the other not to be so, but only that the one seems coloured and the other not. If such a view is to be possible, we shall have, of course, to maintain that the kind of experience which I have expressed by saying one seems different from the other—“seems circular,” “seems blue,” “seems coloured,” and so on—involves an ultimate, not further analysable, kind of psychological relation, not to be identified either with that involved in being “perceived” to be so and so, or with that involved in being “judged” to be so and so; since a presented object might, in this sense, seem to be elliptical, seem to be blue, etc., when it is neither perceived to be so, nor judged to be so. But there seems to me to be no reason why there should not be such an ultimate relation. The great objection to such a view seems to me to be the difficulty of believing that I don’t actually perceive this sense-datum to be red, for instance, and that other to be elliptical; that I only perceive, in many cases, that it seems so. I cannot, however, now persuade myself that it is quite clear that I do perceive it to be so. And, if I don’t, then it seems really possible that this presented object really is identical with this part of the surface of this inkstand; since, when I judge, as in the cases supposed, that the surface in question is not, so far as I can tell, perceptibly different from what it was, I might really be judging of the two sense-data that they also were not, so far as I can tell, perceptibly different, the only difference between the two that is perceptible, being that the one seems to be of a certain size, shape or colour, and the other to be of a different and incompatible size, shape or colour. Of course, in those cases, as in that of the balloon being blown up, where I “perceive” that the surface has changed, e.g. in size, it would have to be admitted that I do perceive of the two sense-data not merely that they seem different in size, but that they are so. But I think it would be possible to maintain that the sense in which, in these cases, I “perceive” them to be different, is a different one from that in which, both in these and in the others, I perceive them to seem so.

Possibly in making this suggestion that sense-data, in cases where most philosophers have assumed unhesitatingly that they are perceived to be different, are only really perceived to seem different, I am, as I said, talking sheer nonsense, though I cannot, at the moment, see that I am. And possibly, even if this suggestion itself is not nonsense, even if it is true, there may be other fatal objections to the view that this presented object really is identical with this part of the surface of this inkstand. But what seems to me certain is that, unless this suggestion is true, then this presented object is certainly not identical with this part of the surface of this inkstand. And since it is doubtful whether it is not nonsense, and still more doubtful whether it is true, it must, I think, be admitted to be highly doubtful whether the two are identical. But, if they are not identical, then what I am judging with regard to this presented object, when I judge “This is an inkstand,’’ is certainly not that it is itself part of the surface of an inkstand; and hence, it is worth while to inquire further, what, if I am not judging this, I can be judging with regard to it.

And here, I think, the first natural suggestion to make is that just as, when I talk of “this inkstand,” what I seem really to mean is “the inkstand of which this is part of the surface,” so that the inkstand is only known to me by description as the inkstand of which this material surface is part of the surface, so again when I talk of “this material surface,” what I really mean is “the material surface to which this (presented object) has a certain relation,” so that this surface is, in its turn, only known to me by description as the surface which has a certain relation to this presented object. If that were so, then what I should be judging of this presented object, when I judge “This is part of the surface of an inkstand,” would be not that it is itself such a part, but that the thing which stands to it in a certain relation is such a part: in short, what I should be judging with regard to it, would be “There’s one thing and one only which stands to this in this relation, and the thing which does so is part of the surface of an inkstand.”

But if we are to adopt the view that something of this sort is what we are judging, there occurs at once the pressing question: What on earth can the relation be with regard to which we are judging, that one and only one thing stands in it to this presented object? And this is a question to which, so far as I know, none of those philosophers, who both hold (as many do) that this presented object is not identical with this part of the surface of this inkstand, and also that there really is something of which it could be truly predicated that it is this part of the surface of this inkstand (that is to say, who reject all views of the Mill-Russell type), have given anything like a clear answer. It does not seem to have occurred to them that it requires an answer, chiefly, I think, because it has not occurred to them to ask what we can be judging when we make judgments of this sort. There are only two answers, that I can think of, which might be suggested with any plausibility.

Many philosophers, who take the view that the presented objects about which we make these judgments are sensations of ours, and some even who do not, are in the habit of talking of “the causes” of these objects as if we knew, in the case of each, that it had one and only one cause; and many of them seem to think that this part of the surface of this inkstand could be correctly described as the cause of this presented object. They suggest, therefore, the view that what I am judging in this case might be: “This presented object has one and only one cause, and that cause is part of the surface of an inkstand.” It seems to me quite obvious that this view, at all events, is utterly untenable. I do not believe for a moment, nor does any one, and certainly therefore do not judge, that this presented object has only one cause: I believe that it has a whole series of different causes. I do, in fact, believe that this part of the surface of this inkstand is one among the causes of my perception of this presented object: that seems to me to be a very well established scientific proposition. And I am prepared to admit that there may be good reasons for thinking that it is one among the causes of this presented object itself, though I cannot myself see that there are any. But that it is the only cause of this presented object I certainly do not believe, nor, I think, does anybody, and hence my judgment certainly cannot be “The cause of this is part of the surface of an inkstand.” It might no doubt, be possible to define some kind of causal relation, such that it might be plausibly held that it and it alone causes this presented object in that particular way. But any such definition would, so far as I can see, be necessarily very complicated. And, even when we have got it, it seems to me it would be highly improbable we could truly say that what we are judging in these cases is: “This presented object has one and only one cause, of this special kind.” Still, I do not wish to deny that some such view may possibly be true.

The only other suggestion I can make is that there may be some ultimate, not further definable relation, which we might for instance, call the relation of “being a manifestation of,” such that we might conceivably be judging: “There is one and only one thing of which this presented object is a manifestation, and that thing is part of the surface of an inkstand.” And here again, it seems to me just possible that this may be a true account of what we are judging; only I cannot find the slightest sign that I am in fact aware of any such relation.

Possibly other suggestions could be made as to what the relation is, with regard to which it could be plausibly supposed that in all cases, where we make these judgments we are in fact judging of the presented object “There is one and only one thing which stands to this object in this relation.” But it seems to me at least very doubtful whether there is any such relation at all; whether, therefore, our judgment really is of this form, and whether therefore, this part of the surface of this inkstand really is known to me by description as the thing which stands in a certain relation to this presented object. But if it isn’t, and if, also, we cannot take the view that what I am judging is that this presented object itself is a part of the surface of an inkstand, there would seem to be no possible alternative but that we must take some view of what I have called the Mill-Russell type. Views of this type, if I understand them rightly, are distinguished from those which I have hitherto considered, by the fact that, according to them, there is nothing whatever in the Universe of which it could truly be predicated that it is this part of the surface of this inkstand, or indeed that it is a part of the surface of an inkstand, or an inkstand, at all. They hold, in short, that though there are plenty of material things in the Universe, there is nothing in it of which it could truly be asserted that it is a material thing: that, though, when I assert “This is an inkstand,” my assertion is true, and is such that it follows from it that there is in the Universe at least one inkstand, and, therefore, at least one material thing, yet it does not follow from it that there is anything which is a material thing. When I judge “This is an inkstand,” I am judging this presented object to possess a certain property, which is such that, if there are things, which possess that property, there are inkstands and material things, but which is such that nothing which possesses it is itself a material thing; so that in judging that there are material things, we are really always judging of some other property, which is not that of being a material thing, that there are things which possess it. It seems to me quite possible, of course, that some view of this type is the true one. Indeed, this paper may be regarded, if you like, as an argument in favour of the proposition that some such view must be true. Certainly one of my main objects in writing it was to put as plainly as I can some grave difficulties which seem to me to stand in the way of any other view; in the hope that some of those, who reject all views of the Mill-Russell type, may explain clearly which of the alternatives I have suggested they would adopt, or whether, perhaps, some other which has not occurred to me. It does not seem to me to be always sufficiently realised how difficult it is to find any answer to my question “What are we judging in these cases?” to which there are not very grave objections, unless we adopt an answer of the Mill-Russell type. That an answer of this type is the true one, I am not myself, in spite of these objections, by any means convinced. The truth is I am completely puzzled as to what the true answer can be. At the present moment, I am rather inclined to favour the view that what I am judging of this presented object is that it is itself a part of the surface of an inkstand—that, therefore, it really is identical with this part of the surface of this inkstand, in spite of the fact that this involves the view that, where, hitherto, I have always supposed myself to be perceiving of two presented objects that they really were different, I was, in fact, only perceiving that they seemed to be different. But, as I have said, it seems to me quite possible that this view is, as I have hitherto supposed, sheer nonsense ; and, in any case, there are, no doubt, other serious objections to the view that this presented object is this part of the surface of this inkstand.